The invention relates to a bimodal, styrenic polymer foam structure having enhanced insulative properties.
A foam structure with a bimodal cell size distribution has a distribution of relatively larger primary foam cells and relatively smaller secondary foam cells. Most conventional foam structures have a unimodal or primary cell size distribution only. Various foam structures with bimodal cell distributions are seen in U.S. Pat. Nos. 4,455,272 and 4,559,367 and in European Patent Application 89114160.8.
Bimodal foam structures offer advantages over conventional unimodal foam structures. The advantages include greater toughness and enhanced insulating capability. Further, bimodal structures are typically made using water as a blowing agent component and unimodal structures typically are not. Since use of water as a blowing agent component is desirable for environmental reasons, the manufacture of bimodal structures is similarly desirable.
It would be desirable to further enhance the insulating capability of the bimodal foam structures. It would be further desirable to increase such insulating capability without detrimentally affecting the physical properties of the foam structure or detrimentally affecting its manufacture or processing.